© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Industrial Engineering and Ergonomics
Dr.-Ing. Dr. rer. medic. Dipl.-Inform. Alexander Mertens
Univ.-Prof. Dr.-Ing. Dipl.-Wirt.-Ing. Christopher M. Schlick
Chair and Institute of Industrial Engineering and Ergonomics
RWTH Aachen University
Bergdriesch 27
52062 Aachen
phone: 0241 80 99 494
email: [email protected]
Unit 5
Modeling and optimizing manual work processes with MTM
Fall Winter 2016/2017
5 - 2 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Learning Targets
Learning the basic principles of the sequence-analytical time modeling (predetermined motion-time systems) of manual work processes
Getting to know and generally being able to independently apply MTM (“Methods-Time Measurement”)
Being acquainted with compressed MTM data systems
Being capable of choosing the correct MTM data system in practice
Being acquainted with the possibilities and limitations in the usage of MTM
5 - 3 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Introduction: Automobile assembly
How to conduct “line-
balancing” of manual tasks in
an assembly line, so that the
utilisation is as high as
possible without constraining
the employees by the process
design?
Work station 1 W 1.1
Work station 2
W 2.2
Work station 3
W 2.1.1
W 2.1.2
W 2.3
...
Clock cycle
W 1.2
W 1.3
Illustration for line-
balancing
(Gantt chart)
Source: DPA; Spiegel Online 2008 M
ate
rial flow
5 - 4 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Methods for the determination of time data
Determining time
experimental methods (ACTUAL TIMES)
computational methods (TARGET TIMES)
observation
• manual time measurement - stopwatch - video analysis - REFA procedures
• work sampling (time measurement by means of statistical analysis)
– frequencies (MMH) – time-on-task (MMZ)
• interview techniques
self-report
• made by the worker
comparison and estimation
• Comparison of the work procedures for which the time standards are to be determined with similar activities for which time standards have already been set.
• The estimation is based on standard times for the proce- dure based on historical records or experience (comparative estimation).
compilation
calculation of work cycles
• systems of predetermined times • based on
process models (e.g., for turning)
• with quantitative information processing models
• with biomechanical models
– list of activities, their duration, and the frequency of their occurrence (e.g., office work)
• with the aid of devices (e.g., computer log-files)
• standard times - catalogue of task times - nomograph
- Methods Time Measurements (MTM) - Work Factor (WF)
Statistical time models Sequence-analytical time models
5 - 5 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
MTM as a Predetermined Motion-Time System
The method
determines the
time
Methods
Time
Measurement
MTM is a predetermined motion-time system (PMTS).
Predetermined motion-time systems are methods to fractionalize manual
operational procedures, which can be influenced by the worker, in elements of
motions and to assign motion time standards to these elements.
2 3 4 5
time
Motion element
3
3
4
4
5
5 2
Right hand motion
Left hand motion
1
2 1
1
5 - 6 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Application of Predetermined Motion-Time Systems
(PMTS)
• planning of the
operating process
• optimization of the
operating process
• design of tools and
equipment
• design of the
manufacture
• creation of target
times
• determination of
standard time for
performance-related
wages
• pre-costing
• description of the
operating processes
for education and
instruction materials
PMTS applications
work instruction time determination design of the work
system
5 - 7 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Historic milestones in the development of PMTS
1900
1910
1920
1930
1940
1950
F. W. Taylor: Scientific Management (fractionalization of tasks and measurement of subtracted
times)
F. B. Gilbreth (1911) Motion Study
R. Thun (1925) (proposals for the development of a system of
pre-determined times)
(Gilbreth detected that human motions can be put down to
seventeen fundamental motions - Therbligs - by dint of film
shots.)
WF (Work Factor): Start of development (1934)
WF published in 1945 (Quick et al.)
MTM: Start of development (1940)
MTM published in 1948
(H. B. Maynard, J. L. Schwab, G. J. Stegemerten)
1970 MOST published in 1972 (K. Zandin)
5 - 8 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Development of MTM-1 - Procedure
Acquisition of motion sequences and their influencing variables
in different work situations with different workers by means of
film shots
(single pictures with a rate of 16 pictures per second)
Determination of actual times by counting single pictures
Compensation of interpersonal performance variation by using
the Lowry-Maynard-Stegemerten (LMS) method
Compensation of variance by regression analysis
Result: MTM-1 metric card
5 - 9 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
influences independent
from people
effort dexterity constancy of
execution time
working
conditions (e.g. lightning)
influences dependent
from people
performance index
according to LMS
= actual time according
to video analysis /
time recording
median LMS-
performance index of
the evaluation group
MTM standard
performance
A standard performance of 100% is described within the LMS method as
“performance of a moderately high trained person who can show this
performance in perpetuity without work fatigue”.
Development of MTM-1 -
The Lowry-Maynard-Stegemerten method
LMS: Lowry, Maynard, Stegemerten
(names of the developers of this
method)
5 - 10 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Development of MTM-1 -
Results
Result of the development:
MTM-1 metric card
The MTM-1 metric card
comprises time values for
fundamental motions subject to
time-influencing factors
Time values are stated as TMU
(Time Measurement Unit)
1/100,000 h = 1 TMU
0.036 s = 1 TMU
Deutsche MTM-
Vereinigung e.V.
5 - 11 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
MTM-1:
Fundamental motions at a glance (1a)
5 fundamental motions of the finger-, hand-, and arm-system
Release Reach
Grasp
Move
Position
Deutsche MTM-
Vereinigung e.V.
Motion
cycle
5 - 12 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
MTM-1:
Fundamental motions at a glance (1b)
The performance of
simple motions such as
Reach and Move can
hardly be improved by
means of additional
training.
Difficult motions such
as Grasp and Position
are available for training
and can thereby be
improved.
(Source: Rohmert & Kirchner, 1969)
Comparison of the learning progress for the different motions:
time per
motion
Grasp
Reach
Position
Move
person A
person B
person C
training time training time
5 - 13 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
3 additional fundamental motions of the
finger-, hand-, and arm-system:
Turn
MTM-1:
Fundamental motions at a glance (2)
Disengage
Apply Pressure
Resistance which is
to be overcome to
open the fridge’s
door
Deutsche MTM-
Vereinigung e.V.
5 - 14 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
2 fundamental motions of the eyes:
D = 30 cm
T =
4 0
c m
MTM-1:
Fundamental motions at a glance (3)
Eye focus
Eye travel
Deutsche MTM-
Vereinigung e.V.
5 - 15 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
15 fundamental motions for body movements:
MTM-1:
Fundamental motions at a glance (4)
body
movements
without shift of
body axis
with shift of
body axis
with inclination
of body axis
foot motion
leg motion
side step
turn body
walk
bend
arise from bend
stoop
arise from stoop
kneel on one knee
arise from kneel on one knee
kneel on both knees
arise from kneel on both
knees
sit
stand
5 - 16 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
MTM-1: Time-influencing factors considering
reaching as example
2 or less 2,0 2,0 2,0 2,0 1,6 1,6 0,4
4 3,4 3,4 5,1 3,2 3,0 2,4 1,0
6 4,5 4,5 6,5 4,4 3,9 3,1 1,4
8 5,5 5,5 7,5 5,5 4,6 3,7 1,8
10 6,1 6,3 8,4 6,8 4,9 4,3 2,0
12 6,4 7,4 9,1 7,3 5,2 4,8 2,6
14 6,8 8,2 9,7 7,8 5,5 5,4 2,8
16 7,1 8,8 10,3 8,2 5,8 5,9 2,9
18 7,5 9,4 10,8 8,7 6,1 6,5 2,9
20 7,8 10,0 11,4 9,2 6,5 7,1 2,9
22 8,1 10,5 11,9 9,7 6,8 7,7 2,8
24 8,5 11,1 12,5 10,2 7,1 8,2 2,9
26 8,8 11,7 13,0 10,7 7,4 8,8 2,9
28 9,2 12,2 13,6 11,2 7,7 9,4 2,8
30 9,5 12,8 14,1 11,7 8,0 9,9 2,9
35 10,4 14,2 15,5 12,9 8,8 11,4 2,8
40 11,3 15,6 16,8 14,1 9,6 12,8 2,8
45 12,1 17,0 18,2 15,3 10,4 14,2 2,8
50 13,0 18,4 19,6 16,5 11,2 15,7 2,7
55 13,9 19,8 20,9 17,8 12,0 17,1 2,7
60 14,7 21,2 22,3 19,0 12,8 18,5 2,7
65 15,6 22,6 23,6 20,2 13,5 19,9 2,7
70 16,5 24,1 25,0 21,4 14,3 21,4 2,7
75 17,3 25,5 26,4 22,6 15,1 22,8 2,7
80 18,2 26,9 27,7 23,9 15,9 24,2 2,7
R-E
E Reach to indefinite location to get
hand in position for body balance or
next motion or out of way.
Case and Description
Distanc
e moved
in cm
Time TMU
R-C
R-DR-BR-A
m-Wert
für B
mR-B
R-Bm
D Reach to a very small object or
where accurate grasp is required.
mR-A
R-Am
A Reach to object in fixed location,
or to object in other hand or on
which other hand rests.
B Reach to single object in location
which may vary slightly from cycle to
cycle.
C Reach to object jumbled with
other objects in a group so that
search and select occur.
2. Case of motion
3. Type of
motion path
1. Distance moved “Reach” (R) is the fundamental movement
for moving the fingers or hand to a determined or
undetermined location. Messpunkt
Messpunkt
Bewegungslänge in cm
Messpunkt
Messpunkt
Bewegungslänge in cm
Pictured example: R-B
v
t
v
t
v
t
v
t Typ II
R30Bm mR30B
v
t Typ I
R30B
5 - 17 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
MTM-1: Time-influencing factors considering
grasping as example
“Grasp” (G) is the fundamental motion which is
accomplished to keep one or several items in check
with fingers or hand, so that the following fundamental
motion can be carried out.
Case TMU
G1A 2,0 Pick Up Grasp:
G1B 3,5
G1C1 7,3 > 12 mm Ø
G1C2 8,7 6 to 12 mm Ø
G1C3 10,8 < 6 mm Ø
G2 5,6
G3 5,6
G4A 7,3
G4B 9,1
G4C 12,9
G5 0,0
Description
Very small object or object lying close against a flat surface.
Small, medium or large object by itself, easily grasped.
Regrasp. Shift of the control point of an item without losing control of item
Transfer Grasp. One hand takes over control of an item while other releases.
Contact, sliding or hook grasp. Gain sufficient control over item through
contact so that following fundamental movements can be executed.
Interference with grasp on bottom and one side of nearly
cylindrical object.
< 6x6x3 mm
Select grasp:
Object jumbled with other objects so search
and select occur.
> 25x25x25 mm
6x6x3 bis 25x25x25 mm
Time-influencing
factors:
1. Mode of
grasping
2. Position of item
3. Constitution of
item
5 - 18 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Pick up grasp G 1
Regrasp G 2
Transfer grasp G 3
Select grasp G 4
MTM-1: Time-influencing factors considering
grasping as example
Seldom in practice Frequent in practice Highly frequent in
practice
G 1 A G 1 B G 1 C
Start of motion Motion End of motion
Right hand (dashed) to
left hand Handing over
Right hand (dashed)
has taken on check on
the item.
G 4 A G 4 B G 4 C
Two partial dimensions should fall in the respective category.
> 25 x 25 x 25 mm > 6 x 6 x 3 mm
< 25 x 25 x 25 mm < 6 x 6 x 3 mm
7,3 TMU 9,1 TMU 12,9 TMU
5 - 19 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Application of MTM-1:
Procedure
Motion analysis
Segmentation of the motion sequence in
elements, i.e. reaching.
Time analysis
Determination of the time-influencing factors for
every single motion element, i.e. distance moved,
or property of item.
Coding
of the motion element and of the influencing
variables.
Addition
of the elementary motion times to obtain the basic
motion time in demand.
Extraction
of the elementary motion time from the charts.
5 - 20 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Reach
for bolt • Distance moved: 40 cm
• bolt is mixed with others
R 40 C 16,8 TMU
Grasp
at bolt
• admeasurements: 8 x 12 mm
• bolt is mixed with others G 4 B 9,1 TMU
Move
the bolt to
apparatus
• Distance moved: 40 cm
• accuracy of placing: move object
to exact
location
M 40 C 18,5 TMU
Position
the bolt
to hole
• assembling tolerance: tight
• symmetry: fully symmetric
• handling: easy
P2SE 16,2 TMU
Release
of bolt
• opening the fingers RL 1 2,0 TMU
Description of the
motion sequence
Necessary information for the
time allocation
Coding Time Value
Cumulative time
needed
62,6 TMU
2,25 s
Application of MTM-1:
Example
5 - 21 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Application of MTM-1:
Systematics of the Motion Sequence (1)
simultaneous
movements
combined
movements
successive movements non-successive movements
Motion sequence
Successive movements are single
movements or movements in a
series which are executed
consecutively by the same or
different body parts without
temporal overlapping and
interruption.
Description A H Code TMU Code A H Description
12.8 R30B pens
2.0 G1A
15.1 M30C device
5.6 P1SE
2.0 RL1
5 - 22 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Application of MTM-1:
Systematics of the Motion Sequence (2)
simultaneous
movements
combined
movements
successive movements non-successive movements
Motion sequence
Combined movements are two
or more completed
movements that are executed
at the same time by one body
part.
In the example, a non time-determinig re-grasping (with the same hand) occurs during the movement.
TMU Code A H Description
9.1 G4B
10.5 (M16C device
(G2
5.6 P1SE
5 - 23 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Application of MTM-1:
Systematics of the Motion Sequence (3)
simultaneous
movements
combined
movements
successive movements non-successive movements
Motion sequence
Simultaneous movements are single
movements or movements in a series
that are executed by different body parts
at the same time.
Left hand Right hand
Description A H Code TMU Code A H Description
pens R20C 11.4 [R10C pens
9.1 G4B
G4B 9.1
device M16C) 10.5 (M16C device
G2) (G2
P1SE 5.6 P1SE
RL1 2.0 RL1
5 - 24 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Application of MTM-1:
Systematics of the Motion Sequence (4)
Degree of control of
basic movements
Degree of practice of the
worker
State of the site/ the
objects
Determining criteria for
the simultaneity of
movements:
Read-off example for the simultaneity of movements:
easy
with practice
difficult
Possibilities for
simultaneous execution:
Reach
Move
Grasp
Position
Disengage
Disengage Position Grasp Move Reach
within normal field of view
outside normal field of
view
Easy to handle
Difficult to handle
V5-1 Bimanual movements
5 - 25 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Example of application: Assembly of two bolts –
Analysis using MTM-1
Reach R30C 14,1 TMU
Grasp G4B 9,1 TMU
Move M30C 15,1 TMU
Position P2SE 16,2 TMU
Release RL1 2,0 TMU
Reach R30C 14,1 TMU
Grasp G4B 9,1 TMU
Move M30C 15,1 TMU
Position P2SE 16,2 TMU
Release RL1 2,0 TMU
Total Time 113 TMU
left hand right hand
R30C 14,1 TMU R30C
G4B 9,1 TMU
9,1 TMU G4B
M30C 15,1 TMU M30C
16,2 TMU P2SE
P2SE 16,2 TMU
RL1 2,0 TMU RL1
81,8 TMU
5 - 26 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Possibilities and limitations in the application
of MTM-1
Application of MTM-1
mass production in large batches
limited product variety
short-cyclical workflows
exactly defined basic conditions
experienced, highly trained employees
workstations with a detailed-oriented design
comparison
of
processes
comparison
of design
alternatives
process
optimization
evaluation
of short-
cyclical
workflows
creation
of the
work plan
and training
5 - 27 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Further development of MTM (1)
change of the
market
requirements for
analysis systems
objectives of
further
development
shortening of the
product-life-cycles
increase in the
number of
alternatives
smaller batch sizes
frequently-changing
production requests
high analysis
speed
sufficient
accuracy of
the time data
transparency and
reproducibility
of the time data
accommodation to the
method level in the following
areas of application:
single-part and
small-series production
series production
5 - 28 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
MEK -
stages of
extension
MEK
UAS -
stages of
extension
MTM-1 fundamental motion
sequence of motions
fundamental operation
steps of operation
sequence of operation
work process
UAS
values of production area
basic values
single-part/
small-series series production mass production
method level low high
data
com
pre
ssio
n
Universal Analyzing System
MTM for single-part and small- series production (MEK)
Further development of MTM (2)
Deutsche MTM-Vereinigung e.V.
5 - 29 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
MTM-1
Get and Place
MTM standard data /
basic values
MTM-UAS/
-MEK
sequence of
motions
fundamental
operations
Reach
Grasp
Move
Position
Release
Get
Place
fundamental motions
Further development of MTM (3)
Data construction by high and transverse
aggregation
Deutsche MTM-
Vereinigung e.V.
5 - 30 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Application Example: Comparision of MTM-1 and
MTM-UAS at a soldering process
Description Code TMU
Get and Place AC2 55
Handle the soldering
iron HC2 70
Soldering PT 100
Release PA2 20
Total 245
MTM-1 MTM-UAS
Left hand Right hand
Description Code TMU Code
Reach R30B 12,8 [R35A
Grasp G1A 2,0 G1A
Move M30C 15,1
Move 16,8 M35C
Position P2SE 16,2
Position 43,0 P3SE
Soldering PT 100,0
Move M30B] 16,8 M35C
Position 5,6 P1SE
Release RL1 2,0 RL1
Gesamt 230,3
5 - 31 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Application example:
Carburetor of type Stromberg 175 CD-2
MTM-1 MTM-UAS
Predicted assembly time 140s 146s
Number of MTM components 975 182
Comparison of MTM-1 and MTM-UAS using the example of
learning process of the subassembly of a carburetor
0 250 500 750 1000
146
T [s]
n
industrial mechanic,
graphical work plan
1 2 3 4 5
146
291
603
TUAS =
T1 =
TUAS =
T [s]
T5 =
n
5 - 32 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Advantages and disadvantages of the MTM
methodology
Advantages
It is possible to determine operating processes and execution times explicitly already in the planning phase of a work system.
Training periods can be reduced since employees can already be trained before the introduction of new work processes.
It is possible to design work systems in a target-oriented way, as influencing variables concerning the execution times become transparent by means of the MTM methodology.
MTM time values are based on a 100% standard performance. An evaluation of the performance rate – as to be found in REFA Stop watch time study – is not necessary.
The coding of the motion elements leads to an internationally homogenous, reproducible description of the operational procedures.
Disadvantages
The implementation of MTM is limited to manually operated tasks.
The analysis effort is rather high.
The analysis can be influenced subjectively.
V5-2 Final example
5 - 33 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Quick Knowledge Check
What is the purpose of predetermined motion-time systems?
What was the procedure during the development of MTM-1?
Which 5 fundamental motions of the finger-, hand-, and arm-system
can be distinguished within MTM-1?
What is the procedure for the application of the MTM method?
What are the preconditions for the application of MTM-1?
What are the reasons for the development of compressed
MTM methods?
How do you determine which MTM analyzing system should
be applied in operational practice?
What are the advantages and disadvantages of the MTM method?
5 - 34 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
References
Antis, W.; Honeycutt, J.M.; Koch, E.N. (1973): The Basic Motions of MTM, The Maynard Foundation, fourth
edition.
Bokranz, R.; Landau, K. (2006): Produktivitätsmanagement von Arbeitssystemen – MTM-Handbuch, Schäffer-
Poeschel Verlag Stuttgart.
Gilbreth, F.B. (1911): Motion Study: A Method for Increasing the Efficiency of the Workman, Van Nostrand, New
York.
Jeske, T.; Schlick, C. (2012): A New Method for Forecasting the Learning Time of Sensorimotor Tasks. In:
Advances in Ergonomics in Manufacturing, S. 241-250, Boca Raton (FL).
Maynard, H.B.; Stegemerten, G.J.; Schwab, J.L. (1948): Methods-time Measurement. McGraw-Hill Book
Compony, New York.
Rohmert, W.; Kirchner, J.H. (1969): Anlernung sensumotorischer Fertigkeiten in der Industrie. Beuth, Berlin.
Salvendy, G. (2001): Handbook of Industrial Engineering, Wiley-Interscience, New York, N. Y. 10158, third
edition.
Schlick, C.; Bruder, R.; Luczak, H. (2010): Arbeitswissenschaft, Springerverlag Berlin Heidelberg.